I. Introduction to

Acids & Bases

Unit 14- Acids & Bases

A. Properties

electrolytes electrolytes

turn litmus red

sour taste

react with metals

to form H2 gas

slippery feel

turn litmus blue

bitter taste

ChemASAP

vinegar, milk, soda,

apples, citrus fruits

ammonia, lye,

antacid, baking soda

3 Definitions of Acids

Arrhenius: acids are substances which

produce H+ ions in water.

Brønsted-Lowry: acids are substances

which donate H+ ions to other

substances.

Lewis: acids are substances which

accept electron pairs from other

substances.

3 Definitions of Bases

Arrhenius: Bases are substances that

produce OH- ions in water.

Brønsted-Lowry: Bases are substances

that accept H+ ions from other

substances.

Lewis: Bases are substances that

donate a pair of electrons to another

substance.

B. Definitions

Brønsted-Lowry

HCl + H2O Cl

–+ H

3O

+

•Acids are proton (H+) donors.

•Bases are proton (H+) acceptors.

conjugate acidconjugate base

baseacid

B. Definitions

H2O + HNO

3 H

3O

+ + NO

3

–

CBCAAB

B. Definitions

Lewis

•Acids are electron pair acceptors.

•Bases are electron pair donors.

Lewis base

Lewis acid

Unit 14- Acids & Bases

II. pH

A. Ionization of Water

H2O + H2O H3O+ + OH-

Kw = [H3O+][OH-] = 1.0 10-14

A. Ionization of Water

Find the hydroxide ion concentration of

3.0 10-2 M HCl.

[H3O+][OH-] = 1.0 10-14

[3.0 10-2][OH-] = 1.0 10-14

[OH-] = 3.3 10-13 M

Acidic or basic? Acidic

pH = -log[H3O+]

B. pH Scale

0

7INCREASING

ACIDITYNEUTRAL

INCREASING

BASICITY

14

pouvoir hydrogène (Fr.)

“hydrogen power”

B. pH Scale

pH of Common Substances

B. pH Scale

pH = -log[H3O+]

pOH = -log[OH-]

pH + pOH = 14

III. Titration

Unit 14- Acids & Bases

A. Neutralization

Chemical reaction between an acid and

a base.

Products are a salt (ionic compound)

and water.

A. Neutralization

ACID + BASE SALT + WATER

HCl + NaOH NaCl + H2O

HC2H

3O

2+ NaOH NaC

2H

3O

2+ H

2O

• Salts can be neutral, acidic, or basic.

• Neutralization does not mean pH = 7.

weak

strong strong

strong

neutral

basic

Acid-Base Titrations

A titration is a volumetric technique

often involving acid-base

neutralizations.

It often involves reacting one solution

of known concentration, with another

of unknown concentration.

Let’s take a look at how a titration is

performed.

Then we’ll look at calculations.

Equivalence point (endpoint)

• Point at which equal

amounts of H3O+ and OH-

have been added.

• Determined by…

• indicator color change

B. Titration

• dramatic change in pH

B. Titration

moles H3O+ = moles OH-

MVn = MVn

M: Molarity

V: volume

n: # of H+ ions in the acidor OH- ions in the base

B. Titration

42.5 mL of 1.3M KOH are required to

neutralize 50.0 mL of H2SO4. Find the

molarity of H2SO4.

H3O+

M = ?

V = 50.0 mL

n = 2

OH-

M = 1.3M

V = 42.5 mL

n = 1

MV# = MV#

M(50.0mL)(2)

=(1.3M)(42.5mL)(1)

M = 0.55M H2SO4